Non-ionic surfactant derivatives of perfluoro alkane-sulfonamides



NON-Ionic SURFACTANT DERIVATIVES on Y IPERFLUORO ALKANE-SULFONAMIDES 5"rain it. Ahlbrecht, White Bear Lake, and Duane E. I

I Morin, St. Paul, Minn., assignors to Minnesota Mining fandManufacturingCompany, St..Paul,'Minn., a corporation 'of'Delawai-e I I1N0 Drawing. Application July 23, 1951' 5 Serial No. 673,565

5 Claims. (Cl. 260-556) This invention relates to non-ionic surfactantsand more particularly to certainN-(polyoxa-alkyl)-perfiuoroalkanesulfonamides.

Substances which in small amounts, radically depress the surface tensionof their solutions below that of the solvent are. termed surface activeand as a broad class Lare'knoivnfas surfactants. These arefrequently'characterized by the presence of a large lipophilicend-portion and a'sm'alllipophobic but hydrophilic ionized portion.

:The li'pophilicQ portion then tends to dissolve only in hydrocarbon ornon aqueous phases while the lipophobic portion'is soluble'in'aqueousphases. In theabsence of a non-aqueous phase there is a tendency forthese mole- H I h The value of n is controllable by variations in theamount -of ethylene orpropylene oxide used as well as the temcules toaccumulate at interfaces, either of water'to air .orwater to containerwalls. Because of their dual nature, i su'rfactants ofthis'type. areuseful emulsifiers and dispersants.

1 (In the, new field of fiuorochemical monomers it has ,be'en'found,that fluorocarbons commonly do not have 'lipo'philic charactersnor arethey hydrophilic, They are both oleophobic'and hydrophobic; For theemulsion polymerization of fluorocarbon monomers, ordinary surfactantsare generally inadequate. unore teflficient emulsifying; agentis .onewhich possesses a hydrophilic end together with a portion'which has.aflinity :for fluorinated materials ,which may be conveniently-betermed fiuophilic'. For example, fluorocarbon In such systems, a

.endshave greateraflinityfor highlyfluorinated materials J I .thanid othe more conventional lipophilic portions of the lus'ualsurface-active.agents such as sodium lauryl sulfate.

isan object of this invention-to provide novel surfactant'compounds." Itis another. object of the invention to' provide s'urfaceactiveagentspossessing both a hydrophilic portion and a fiuophilic portion.Other objects of the invention will become evident from the disclosureset forth hereinafter.

' According to the above andother objects of the invention, it has beenfound that N-(polyoxa-alkyD-perfluoroalkane sulfonamides which can berepresentedv by the general formula;

RrSOr-N-R carbon atoms, is a member of the group consisting of hydrogen,lower alkyl'radicals and R; and R is a polyoxa-alkyl group having theformula:

RI! f onnmqoomdn ..+o-R" inIwhich'rii'is'an integer from two to three, nis a number from two to about twenty, and each R" is hydrogen or amethyl radical, are surface active agents of excepit onalactivit-y.Inaddition to possessing the general de- .,s irable' characteristicsofhigh surface activity, they are particularly useful in emulsifyingfiuorochemical monoe'rs, as, fol-example, in producing elastomers ofhigh o l ;res stance by emulsionpolymerization processes.

f atented Dec. 1, 1959 They possess the further advantage of-beingnon-ionic so that their surfactant activity is substantially independentof pH over wide ranges.

As solutes in minute amounts the compounds of the invention aresurprisingly elfective in lowering the surface tension of water, and areextremely useful where that effect is desired; as well as foremulsifying agents .or as surfactants in compositions such as floor wax,to

produce leveling effects. They also find utility as additives to aqueoussolutions used in the treatment of textiles, paper, leather and othermaterials, as well as additives for petroleum products.

Broadly speaking, the N-polyoxa-alkyl-perfiuoroalkanesulfonamides of theinvention can be prepared by the condensation in.- alkaline medium ofethylene or propylene oxideand an appropriately substitutedperfluoroalkylsulifonylamidoalkanol (produced by the method of Ahl-'brecht and.-Brown, described in application Ser. No. 560,-

899, filed January 23., 1956, now U.S. Patent 2,803,656). The followingequation illustrates the course of the reac tion:

perature and duration of the reaction from 2 or 3 to an average of 20or'more. Alternatively, the sodium salt of a perfluoroalkanesulfonamide,of the type described in U.S.- Patent No. 2,732,398, can be condensedwith a polyethylene glycol halidehaving the desired number of molesofethylene oxide. The following equation, showing the preparation of thecondensation product of N- -methyhperfluoro-dodecancsulfonamide with apolyethylene glycol chloride of molecular weight about 365, illus-Another method for preparation of the compounds of the invention whichhave terminal methoxy groups on the polyoxyalkylene moiety, comprisesthe condensation of a perfluoroalkanesulfonyl fluoride such as thosedescribed in U.S. Patent 2,732,398, with a polyglycolamine 'having thedesired 'chain length.

perfiuorooctanesulfonamide, N isopropyl perfiuorooctanesulfonamide, Nethyl perfluorododecanesulfonamide and perfluorodecanesulfonamide. 'Thepolyalkylene glycol halides which are reacted with'these compounds areconveniently identified as to chain length by their molecular'weight.For example, a polyethylene glycol chloride of average molecular weight410 contains about 8 to 9 condensed ethylene oxide units; one of averagemolecular weight 610 contains about 13 cont 3 densed ethylene oxideunits; one of average molecular weight 975 contains about 22 condensedethylene oxide units, and so on.

The following examples, which are illustrative only rather than limitingor delineative of the scope of the invention, serve to describe thenovel compounds, their method of preparation and their properties.

Example 1 A flask fitted with a mechanical stirrer, a gas inlet tube anda reflux condenser cooled with a mixture of acetone and solid carbondioxide was charged with 20 grams (0.035 mole) ofN-ethyl-N-Z-hydroxyethyl perfiuorooctane sulfonamide 2 a CaFnSOrNCHzCHzOH and 0.8 gram of 50% sodium hydroxide (0.01 mole). Ethyleneoxide gas was passed into the flask, the temperature of the reactantsbeing held at about 90 to 110 C., for 4 hours. A total of 15.5 grams(0.35 mole) of ethylene oxide was absorbed, indicating the formation ofa polyether of the approximate formula:

The product was a substantially colorless viscous oil at roomtemperature which was more fluid at elevated temperatures.

By repeating this procedure, using about 21 grams of propylene oxide,there is obtained a similar colorless, viscous oil consisting of thecondensation product of propylene oxide and N-ethyl-N-Z-hydroxyethylperfluoro- Surface tension Concentration surfactant (percent)(dynes/cm.)

The surface tension of pure water is about 74 dynes/cm. at 18 C. V

For comparison, there are tabulated surface tension values heretoforedetermined for several known surfactant compounds, as set forth in U.S.Patent No. 2,723,999:

Concen- Surface tration Compound (percent) Condensation product ofhetpafluorobutanol and 4.3 moles of ethylene oxide CF;(CF;):CH:O- 2 40)1 Is apropyl-nuphthalene Sodium sulionate Diisobutyl sodiumsnll'osuccinate..- Diamyl sodium sullosuccinate Latices were preparedfrom 1,1-dihydroperflorohexyl methacrylate in water-acetone mixturesusing C F SO N C H -CI -I CH (OCH CH OH as the emulsifying agent. Onehundred parts by weight of monomer mixed with 180 parts of acetone-watermixture, 0.5 partof the above-named emulsifier andi0.5 part of potassiumpersulfate were heated in a sealed glass container for about 20 hours at50 C. In three different runs, in which 10, 20 and30,% by weight ofacetone were used respectively in the acetone-water fimixture, laticesconsisting of poly-1,l-dihydroperfluorohexyl methacrylate were obtainedin substantially quantitative yield with small amounts of1precoagulum.

Example Each of the six surfactants of the general formula:

I? cmasomwmem-(oemennron inwhich R was methyl, ethyl and butyl and nhadvaluejs of S9 and about 13 wasprepared byreacting stoichiometricamounts of the N-alkyl perfiuorooctanesulfonamide sodium salt withpolyethylene glycol chlorides of average molecularwe jights 410 (n=8-9)and 610 (rt-:ca. 13). In this way, 26 grams .'(0.05 mole) of CgF -{SON(CH )Na were reacted with 20.5 grams (0.05 more of Cl( CH CH O) I-I(molecular weight about 410) by heating together with swirling. in aflask at until an exothermic [reaction commenced which raised thetemperature to about C. After this reaction had subsided, heating wascontinued at 100 C. for about '2 hours. The product was a heavy viscousliquid. The other five surfactants were prepared in the same manner andwere likewise heavy, viscous liquids.

Example3 A mixture or 7.3 g. 0.02 mole) of the sodium salt ofN-methyl-perfluorobutanesulfonamide and 12.2 g. (0.02 m.) ofpolyethylene glycol chloride 610 (corre- 'sponding approximately toC1(CH CH O) H) was heated on the steam bath for about 1.5 hours; Thesulfonamide salt soon dissolved and a finely divided precipitate formed.The reaction product was a viscous, ambercolored liquid. Surface tensionmeasurements of aqueous solutions ofthis product, determined with a DuNouy tensiometer, gave the following values:

Concentration, gi moles/l. Dynesgm 25 The molecular weight of thismaterial is about 900 and it is evident that it an eflective surfaceactive agent.

Exanzple 4' This example illustrates a further method of synthesis whichis particularly suitable for the preparation of certain compositions ofthis invention which are otherwise difficult to prepare.

In a flask fitted with stirrer, condenser and dropping Co. aspolyglycolamine H-221-M. The exothermic reaction represented by thereaction wherein R, is a perfluoroalkyl group having from 4 to 12 carbonatoms, R is a member of the group consisting of efiected a steadyrefluxing of the ethereal solution. The reaction mixture was allowed tostand for 16 hours after all of the amine had been added and was thenwashed with water and with dilute hydrochloric acid (about 0.5 N). Theorganic layer was concentrated to give a viscous brownish residue ofN-(4,7,10,13-tetraoxatetradecyl) perfluorooctanesulfonamide.

Example 5 This example illustrates'the preparation of addition productsof perfluoroalkane sulfonamides and alkylene oxides, in which twopositions on the nitrogen atom are occupied by polyxoaalkylene groups.

A mixture of about 3.04 g. of perfluorooctanesulfonamide and about 5.3g. of ethylene oxide was placed in a heavy-walled glass ampoule. Theampoule was evacu ated and sealed, and then was heated for about 14hours at about 125 to 128 C. The ampoule was then cooled, the contentswere frozen with liquid air, and the tube was opened. Any unreactedethylene oxide was removed by RgSOrllI-R' hydrogen, lower alkyl radicalsand R', and R' is a poly oxa-alkyl group represented by the formula:

f v (CH2)m-(OCHzCH),,0R"

wherein each R" is a member of the group consisting of hydrogen and themethyl radical, m is an integer of the group consisting of 2 and 3, andn is a number from 2 to 20.

2. A compound represented by the formula:

3. A compound represented by the formula:

(llHs C4FnSOzNCzH4(OCH2CHz) 3-03 4. A compound represtend by theformula:

C F SO NH( CH (OCH CH -OCH 5. A compound represented by the formula:

CzHr (EH2. CsFuSOzN-C:H;(OCH2CH)10OH References Cited in the file ofthis patent UNITED STATES PATENTS 2,677,700 Jackson et a1. May 4, 19542,803,656 Ahlbrecht et al Aug. 20, 1957 FOREIGN PATENTS 513,646 CanadaJune 14, 1955

1. A COMPOUND REPRESENTED BY THE FORMULA: